Would I be able to use a device like this:
With my motherboard which only has USB 2 ports?
It is not a problem if I don't use the full potential yet, for now I just need it to work.
I don't know if it applies to all devices universally but for flash drives it should work at lower speeds, yes. You'll get a message saying you should plug it into a 3.0 similar to plugging a 2.0 in a 1.1.
Yes (Dad has an external 3.0 drive and uses on his ew and old laptop ) (2.0 and 3.0 respectively)
They are always backwards compatable. both SATA and USB